We analyze axisymmetric near-contact motion of two drops under the action of an external force or imposed flow. It is shown that hydrodynamic stresses in the near-contact region that are associated with the outer (drop-scale) flow can qualitatively affect the drainage of the thin fluid film separating the drops. If this far-field stress acts radially inward, film drainage is arrested at long times; exponential film drainage occurs if this stress acts outward. An asymptotic analysis of the stationary long-time film profile is presented for small-deformation conditions, and the critical strength of van der Waals attraction for film rupture is calculated. The effect of an insoluble surfactant is also considered. Hindered and enhanced drop coalescence are not predicted by the current theories, because the influence of the outer flow on film drainage is ignored.

A thin flow-focusing microfluidic channel is evaluated for generating monodisperse liquid droplets. The microfluidic device is used in its native state, which is hydrophilic, or treated with OTS to make it hydrophobic. Having both hydrophilic and hydrophobic surfaces allows for creation of both oil-in-water and water-in-oil emulsions, facilitating a large parameter study of viscosity ratios (droplet fluid/continuous fluid) ranging from 0.05 to 96 and flow rate ratios (droplet fluid/continuous fluid) ranging from 0.01 to 2 in one geometry. The hydrophilic chip provides a partially-wetting surface (contact angle less than 90°) for the inner fluid. This surface, combined with the unusually thin channel height, promotes a flow regime where the inner fluid wets the top and bottom of the channel in the orifice and a stable jet is formed. Through confocal microscopy, this fluid stabilization is shown to be highly influenced by the contact angle of the liquids in the channel. Non-wetting jets undergo breakup and produce drops when the jet is comparable to or smaller than the channel thickness. In contrast, partially-wetting jets undergo breakup only when they are much smaller than the channel thickness. Drop sizes are found to scale with a modified capillary number based on the total flow rate regardless of wetting behavior.

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Fe 2 (OH) 3 Cl Fe(OH) 2 GR(II)SO 4 hibbingite green rust Pitzer model Pure-iron end-member hibbingite, Fe 2 (OH) 3 Cl(s), may be important to geological repositories in salt formations, as it may be a dominant corrosion product of steel waste canisters in an anoxic environment in Na-Cl-and Na-Mg-Cl-dominated brines. In this study, the solubility of Fe 2 (OH) 3 Cl(s), the pure-iron endmember of hibbingite (Fe II , Mg) 2 (OH) 3 Cl(s), and Fe(OH) 2 (s) in 0.04 m to 6 m NaCl brines has been determined. For the reaction Fe 2 ðOHÞ 3 ClðsÞ þ 3H þ ↔3H 2 O þ 2Fe 2þ þ Cl − ; the solubility constant of Fe 2 (OH) 3 Cl(s) at infinite dilution and 25°C has been found to be log 10 K =17.12±0.15 (95% confidence interval using F statistics for 36 data points and 3 parameters). For the reaction FeðOHÞ 2 ðsÞ þ 2H þ ↔2H 2 O þ Fe 2þ ; the solubility constant of Fe(OH) 2 at infinite dilution and 25°C has been found to be log 10 K =12.95±0.13 (95 % confidence interval using F statistics for 36 data points and 3 parameters). For the combined set of solubility data for Fe 2 (OH) 3 Cl(s) and Fe(OH) 2 (s), the Na +-Fe 2+ pair Pitzer interaction parameter θ Na + /Fe 2+ has been found to be 0.08± 0.03 (95% confidence interval using F statistics for 36 data points and 3 parameters). In nearly saturated NaCl brine we observed evidence for the conversion of Fe(OH) 2 (s) to Fe 2 (OH) 3 Cl(s). Additionally, when Fe 2 (OH) 3 Cl(s) was added to sodium sulfate brines, the formation of green rust(II) sulfate was observed, along with the generation of hydrogen gas. The results presented here provide insight into understanding and modeling the geochemistry and performance assessment of nuclear waste repositories in salt formations.

It is shown that self-supporting graphitic structures of specific shape can be grown in a variety of forms, from nanoscale to macroscale, on metal templates, in a fuel-rich mixture of ethylene and oxygen at temperatures between 750 and 900 K. The evidence presented suggests graphite can be grown in any shape created from catalytic metals (e.g., Ni) under the proper conditions of temperature and gas composition. Structures produced include macroscale bodies, centimeters in dimension, composed of micrometer-scale graphite elements such as graphite "foam" and regular graphite "lattices". Nanoscale hollow graphite spheres were also produced. The production rate in the apparatus employed was roughly shown to be 1 layer/s and was steady with time over several hours. The process of producing self-supporting bodies generally produces hollow graphite structures, as the underlying metal template must be removed by acid following the completion of graphite growth. The process is believed to be possible only in an environment, such as combustion, in which a high concentration of particular radical species is present in the vicinity of the template surface. The following process is postulated: (i) a single layer of graphite is formed from gas-phase radicals by the catalytic action of the metal template, (ii) additional graphite growth is "autocatalytic" and occurs via the decomposition of radicals on the surface and the incorporation of "free" carbon atoms, or other radical fragments, into "edge sites" on the graphite surface.